Wednesday, October 12, 2011

What Is Your Slide Number?

Last week, I listened to a colleague give a talk in my department. It was a very interesting talk and I paid close attention, but I was also kind of fascinated by how much time he spent on each slide.

He spends much much more time/slide than I do in a typical talk, and therefore he showed many fewer slides than I would have in a similar talk.

For example, if a talk is 12-15 minutes, he will have no more than 12-15 slides (and more commonly 12 than 15). In a 50 minutes talk, he may have 30 slides. In each case, I would typically have twice that many slides, even for a talk on a similar (or the same) topic. I hasten to note that I typically finish my talks well within the allotted time.

I would not blame you for concluding that I give unintelligible and incoherent talks crammed with too much information, but let's assume, just for the sake of discussion, that my talks are reasonably understandable; or, at least, no less so than talks by this colleague, who is a minimalist (relative to me) when it comes to number of slides in a talk.

What is your slide number? (Ns)

Ns = number of slides in a talk / talk duration (in minutes)

Important note: If you have one or more animations that appear within one slide, you need to count those separately. For example, if you show a slide with a picture of a red circle on it, and then, after discussing the red circle for a bit, you hit a key/push a button/click a mouse and a blue circle appears next to the red circle, that = 2 slides, not just 1, even if they are technically within one slide. If, however, you have a multitude of tiny little modifications that appear with successive but rapid mouse clicks, you could still count that as 2 (but not 1).

Are you a minimalist, moderate, or a maximalist when it comes to the number of slides/talk?

I usually have more slides than the average of my colleagues, and the rate is about 1-1.5 slides/min. I estimate that most people in my field either go for the speed of 0.5 slides/min (good presentation) or 1-2 slides/min (bad presentation). And the reason I think I am not a bad presenter, even though I have a lot of slides, is that I usually try to put one or two points (or less) per slide. There are many slides with just one word.

Side note: what I consider as minimalist is a bit different from your definition. I consider minimalism as something about the design of the slide as opposed to the slide rate.

Since I often use the same slide deck for talks that vary in length from 40 minutes to 140 minutes, I can't say that I have a fixed ratio. One such talk has 45 slides and a recent version of it took 50 minutes, skipping over about 10 of the slides, so 2 minutes per slide seems about right.

Another recent talk had 47 slides in 60 minutes.

In both cases I was counting major slide changes, not minor highlighting changes, which would increase the 47 to 69, or a little less than a minute apiece.

Yesterday I did a 100-minute lecture and used 30 slides. And actually, I was going at a slightly faster pace than I normally do. There are a few slides in there that have equations gradually being added to the slide (so they can see the derivation without being overwhelmed with a wall of equations immediately). So let's say 33 slides for an Ns=0.3. This was a first-year class, in which I may be a little slower than higher-level classes, in which I might have something in the range of Ns=0.5.

For short talks, e.g. at a conference, I normally plan to be in the range of about Ns=0.5 to Ns=1.

It is not a great idea for a minimalist to collaborate on a talk or lecture with a maximalist. Once, co-teaching a class, sent the draft of my slides to my co-instructor. He added a large number of slides to cover material he thought I was missing, and because he thought I had an inadequate number of slides to take up the class time. When I delivered it I only got about half way through the slides before the time was up, and we both ended up frustrated.

Also, I'm a bit surprised to hear you're a maximalist. From what you've posted before, I understand you use a lot of images in your talks or presentations. With images I take a significant amount of time.

For one of my 50-minute classes, I believe I have 8 slides. Three of them are plots of experimental data, which are typical of the data one would obtain on a particular type of experiment in my field. I spend a LONG time on each of them, pointing to various portions of it, talking about the slope, the intercept, the portions where the near-linear relationship stops being linear, the various definitions we use of various properties of each curve, and how the properties change as you change various other parameters.

When I was an undergraduate we were taught 1 minute per slide, allowing time for questions. I have more-or-less followed this over the years but I tend to talk a lot, and always round downwards in order to finish everything. At my current instituion I have found I normally have many MORE slides than most others, and students at this institution are taught to allow 3 minutes per slide. I also have taken a few pedagodic courses over the past few years which teach 5 minutes per slide maximum! But even that seems to be a lot - many of my colleagues use as few as 10 slides for a 90-minute lecture.

I'm sure this is field-specific, but it sounds like you use quite a lot more slides than is the norm in my field! (cross-appointed in physics and chemistry)

I am tending towards minimalism with time; it has been primarily due to more and more undergraduate teaching practice, whereby you are forced to convey information clearly, slowly and with the minimum amount of text etc as possible, but still conveying maximal information. After all, if the audience really wanted the details, surely they would just go read the paper ... (I note this is much more the European way; US talks that I've seen in my field tend to be crammed with lots of detail and lots of slides).

Moderate, with backup slides after the presentation for if people have questions that are really side-issues.

I tend to have more slides than many people in my field, but one of the things I do is have both the tables with numbers and a slide after that sums up each table. This allows me to go through both if nobody is asking questions or just focus on one set or the other set if I'm running short on time.

The ratio changes depending on talk length. I use approx 20 slides for a 15 min talk, 30 for a 30 min talk, and 45 for an hour talk. I think this is due to the differing burden on the audience - while you can expect a high level of attention/ability to process a fast talk to be sustained for 15 min, an hour is too long to sustain that kind of pace.

Minimalist mathematician. Most of the studies that I've read concerning presentations that a smaller number of good slides is better (too many good slides leads to less retention, and poorer slides...) My own experience at talks jibes with the minimalist view. folks with many slides generally have some that make me ask why they wasted my time with that slide. As with all rules, exceptions can be very good talks, but that's rare. [apparently I'm not a minimalist commenter]

I am usually somewhere between 1-2 slides per minute, depending on the slide. Data slides take longer, intro slides less time. I try to have more slides with less information per slide so that it doesn't end up being overwhelming (my hard and fast rule is one concept per slide); my most recent talk ended up being ~35 minutes and there were 47 slides. So, moderate. But with less time (e.g. a 10 min conference talk), I have a lot more slides per minute and end up being a maximalist just to get all the data in.

I'm about N ~ 1.3. I was taught to stick with a 24 point font, so that keeps the words/slide to something reasonable. Also in general I want each slide to have at least one image. If I'm showing a graph, typically it takes up nearly the whole slide: I don't cram lots of graphs into the same slide. Also my talks usually have one or two movies in them.

When I see an N ~ 0.5 talk, my usual impression is that there is way too much information on each slide, and that the font is way too small, and that people in the back of the room can't read it. Apparently from the comments on this blog post, those of you watching my N ~ 1.3 talks probably are having a similar but opposite reaction to my style.

For me, it depends upon whether I'll get the chance to practice the talk before I deliver it (which is rare, but obviously the ideal).

Slides are helpful for the audience --but they're also a distraction. They add to the cognitive load, because people try to listen and read at the same time (or ignore you for a minute while they read ahead). So, when I can, I try to be a minimalist.

But when I'm not going to get to practice the presentation effectively before delivering it, I use more slides just to keep my talk well-structured and on track.

I'm in an allied health/ behavioral science field and it really depends. When I'm writing a research talk I use N~1 as a guide but I have certain expository slides that I've used a lot and know they take longer, and so I account for that. For teaching I'm at about 2 minutes per slide depending on my comfort level with the material - the higher the comfort level, the more I "riff". I tend to keep my slides text-heavy though because when it's time to write and grade an exam, the words on the slide are the only thing concrete I can point to. I'm pleased when "riffing" content makes it into one of their answers but have found I'll just be disappointed if I expect it to be there.

I am a "moderate" on the high end--usually 70 for a 55 minute talk. I always have a heavy intro with slides that each make a single point, have 4-5 joke slides, and also make sure my data slides only make one point.

You can give a good talk or a bad talk with widely differing numbers of slides, but for me having only one point per slide is the easiest.

Fascinating topic! I never realized that there were more or less standard guidelines on this. I used to budget about 2 mins per slide (without counting title and final "group photo" slide), but as I gained experience I have settled to around 1min per slide for short (15min) talks and around 1.5 min for longer (30+ min) talks. Lectures are completely different and usually will have a lot more time per slide. Field: Experimental physics.

But I agree with the many commenters who say it depends on the audience. I'm always fascinated by the professional speech-givers who use few slides (almost all pictures) or sometimes no slides at all. Someone who can give a fascinating hour-long talk without visual props impresses me. Examples: Jane Goodall, Richard Dawkins.

My answer depends a lot on the audience. For teaching, it's 0.5 slides (or less) per minute. When I give a 15 minute talk, I usually have 18 slides with lots of animations so probably ~2/min. For an hour-long seminar, I usually have about 1.5/min with even more animations. I tend to use them to illustrate processes dynamically as I study stuff in 4D. My research slide presentation is at a much faster rate than is typical in my field and yet I have won numerous best presentation awards both as a student and as a professional. I think it depends more on how much you try to cover in a slide and how you use animations and images. My last seminar had only one bulleted list in the 75 slides.

The workshop talk I gave on Monday had 31 slides in 20 minutes, giving a maximalist Ns of 1.5. Most slides either had one point, or a list of examples. There were 2 or 3 more crowded slides. Perhaps maximalist Ns corresponds to more minimalist slide contents.

This is more systemsy computer science.

I think the previous talk I gave was a presentation to our municipal council supporting Light Rail Transit. That was also maximalist, with 19 slides in 10 minutes. However, it didn't have a lot of technical content, and many slides just included a picture.

I try to not use slides when teaching, but there is sometimes material that's not so good to write on the board.

I'd say moderate, with Ns~1 or Ns>1. FWIW, I tend to talk fast. My slides are mostly figures, with very little text and equations, and I talk "around" the figures. I am in a field at the intersection of physics and engineering.

I am strongly minimalist when presenting "new" information---by which I mean a majority of the audience isn't already familiar with the slide. Like many other I heard the "not more than one slide per minute" advice early on.

When I have a situation with a mixed audience some of whom already know the ground work and some of whom do not, however, I tend to start with a set of "background" slides which I may cover very quickly.

The point is for the "not in the know" segment of the audience to get an idea of where the rest of the presentation fits in, and to allow them to understand the whole presentation when they have time to go over the slides at their leisure.

But then, my audience is often (usually) a subset of my collaborators on a Big Science Project (tm), so they can be expected to take the time to go over the slides at their leisure if our work needs to connect. That may be a different situation from those faced by people who don't work with scores or hundreds of other scientists on a single goal.

I'm a maximalist - for a 12 minute conference talk, I'll have about 20-25 slides. Some of those slides will involve just one photo to illustrate a point that takes about 15 seconds to say. I will spend a couple minutes on other slides, such as the first results graph or a model description. I'm in biology/evolutionary ecology.

I take presentation giving very seriously, and for something like a talk, I find you want to be close to 1 for a couple of reasons. Unless your slides are very, very sparse, going through them at 30 seconds or less per slide is going to throw off audience members who are trying to comprehend both the visual and the audio. I'm good at comprehension, but I feel that people who spend that little on all their slides are rushing, and that's not likely good for your whole audience. As for a "minimalist approach" this can work, but only if your slides have a reasonable amount of information and animation is used effectively to keep things moving, because humans have nonexistent attention spans. Even good, academic humans.

Now, in more talks, the average is 1, but the pacing changes throughout. I'll always have more introductory slides, and then I slow way down for data analysis, which is common in most research talks I go to.

For teaching, I often have less slides, but they have more information associated with them and I do use animation effectively,

I think it depends radically on what sort of information you're presenting. If it's visual information (here's a big tumor, here's a smaller tumor), that can go by as fast as you can say what it is. If it's complex data or mathematics (here's a big ugly plot, here's a Fourier transform), then you have to go much slower if you expect the audience to follow.

I learned the N = 1 rule, and the "any slide with an equation counts double" rule. I probably stick to this on average.

This discussion prompted me to delete two slides from the lightning talk I'm giving after lunch. (~8 minutes, still 11 slides. But no math.)

15 minute talk N~1, 1 hour talk N~0.8, 2 hour lecture N~0.25 which of course involves a lot of other talking and reinforcing, so its very variable, but would have to have lots of images and transitions to be N>1.2.Economist.

Moderate (Ns=1) in biological sciences, although I tend to use a lot of transition slides (usually diagrams and summary figures) and sometimes repeat the same figure every few data slides to make my talks flow better.

Moderate. If I'm giving a timed talk, I stick to the one slide per minute rule, but I tend to spend a little less than one minute on each slide, so that ensures that I don't go over and leaves time for questions. My last presentation had 71 slides, was scheduled for 1 hr and 15 minutes and took 1 hr.

Very much a minimalist - in a 20 minute talk, I might have five to eight slides. There will only be a few key quotes or other textual elements.

I try to include as many important illustrations as I can muster, of course, but there aren't a huge amount of images available for my topics so I'd rather have fewer slides and take a bit more time to 'unpack' each.

I can speak for an hour with 10 slides, although I don't always do this. It really depends on the level of abstraction in the subject matter. Very Abstract means long explanations for each small diagram, peppered with historical anecdotes etc.

about 1.5 minutes per slide, which i thought was too many slides, and never thought of as minimalist. And a fair number of my slides are transition slides with only a picture + a few words or a joke or a quote which i flash pretty quickly. Your colleague's speed sounds about similar to mine, or fairly fast.

I recently was in a meeting where the 6 presenters were supposed to talk 10 min each. The 3 people before me were maximalists, the slides sparked a lot of discussion, so from 10 min we got to 45 min each.

Needless to say, my presentation (minimalist, 6 slides for 10 planned, 15 actual minutes) had to get postponed to the next meeting.

I don't understand these people that bring 50 slides for a 10 min presentation. It is so unreasonable.

I'm an Ns~1, an experimental physicist. I think if you are talking to a "specialist" audience, N~2 or more is ok. However, I always find that there is someone in the audience who is behind (I am sometimes that person in talks that are outside of my specific field...I am a chemist turned laser physicist). I think it's best to talk a little below the level of your average audience member. It bugs me when people assume that I know what bizarre acronyms stand for, much less what their significance is.

I don't think it "depends" on the type of talk as much as some people think it does (I do believe it depends on field, though). I think these things are totally characteristic of people and you are either someone who tends to show lots of slides/talk or someone who doesn't.

I'm probably a moderate to minimalist. I try to focus on images and leave text off slides (as I've read studies show too much text on slides actually detracts from understanding). I think the fact that I have so few slides is probably indicative of the fact that I can condense a lot of information into single plots. Some people don't have a way to show their information in just a single plot and have to show many...or in some cases, I'd say it's poor judgement because they *should* condense the information to make it easier to compare but choose not to, for some reason.

Depends! An equation slide or a complicated plot gets 2 min or more, a simpler slide may get <1 min, maybe only 20seconds if it's for a joke or a pretty picture to drive some point home or show off, say, my beach shack in the Caribbean :) I definitely believe that for most slides, if it takes more then ~1-2 minutes to get through it, then there is too much content on that slide, the font is too small or it is too busy and should be broken up.

Yes, everything depends on the exact content, the style of talk and presentation, etc., etc., but the rule of thumb works pretty well as a ballpark guide.

Incidentally; like most people I often repurpose talks and often start to build a slide set by combining a couple of talks and then winnowing out slides. With this method it is crucial to have a reasonable rule of thumb to target, or else it is very easy to go overboard.....

Minimalist - for a 15 min. talk, maybe 5 slides. All slides are for me are placeholders for my information delivery. Bullets are brief, only a few words so that I can elaborate. If I have a figure I will use my green laser pointer to point out aspects of the figure instead of using animation. I only use animation if I am withholding information on data to build up the audience's anticipation for the final results. To be perfectly honest, I really have better things to do with my time than to make slides.

About Me

I am a full professor in a physical sciences field at a large research university. I am married and have a teenaged daughter.
I have the greatest job in the world, but this will not stop me from noting some of the more puzzling and stressful aspects of my career as a science professor.
E-mail (can't promise to reply): femalescienceprofessor@gmail.com